The long range goal of this study is to better understand the organization and function of airway neurons. Airway neurons synthesize and release mediators such as vasoactive intestinal peptide (VIP) and acetylcholine (ACh) which have potent effect in the airways and are involved in mechanisms regulating the airways in health and disease. Sensory and sympathetic nerve fibers may provide inputs to airway neurons and some airway neurons may project to other airway neurons. The structure and distribution of these neural connections are not defined, but a neuroanatomical analysis could provide an explanation for the occurrence of unappreciated neural mechanisms in the airways. Another unstudied aspect of airway innervation is the cellular and molecular biology of airway neurons. Alterations in the level of neurotransmitter expression has been documented in the central and peripheral nervous systems, but the possibility that airway neurons can undergo such changes has not been studied. The specific aims are to: determine if airway neurons are innervated by 1) sensory nerve fibers from the nodose ganglion or 2) postganglionic sympathetic nerve fibers from the superior cervical ganglion; 3) determine the airway projection of intrinsic airway neuron that contain ACh and VIP; 4) examine in vitro changes in the expression and synthesis of ACh and VIP. Ferrets will be used for the entire project. For specific aims 1) and 2), sensory and sympathetic ganglia will be injected with a neuronal tracer. The presence of labeled fibers in airway ganglia will indicate the projection of fibers from the injection site. The association between labeled fibers and neurotransmitters in the ganglion will be determined. The results may show that sensory and sympathetic nerves -are involved in modulating neurotransmission at airway ganglia. Specific aim 3 will use a tracing method to examine the projection of the intrinsic neurons of tracheal ganglia. The results should reveal intrinsic neural pathways that could be involved in local regulation of airway function. Specific aim 4 will examine mechanisms of ACh and VIP synthesis in airway neurons. The findings may indicate that airway neurons regulate airway responses by increasing or decreasing mediator synthesis in response to environmental conditions. This may be a mechanism of maintaining healthy airways and be involved in the pathogenesis of airway disease like asthma. Overall, the proposed studies will provide new understanding about the organization and function of airway innervation.